Transcritical air conditioning circuit with integrated expansion vessel

ABSTRACT

Air conditioning device ( 1 ) with transcritical operating cycle, the device comprising a circuit ( 4 ) conveying a refrigerant ( 5 ) and successively connecting:
         the outlet ( 6 ) of a compressor ( 7 );   a gas cooler ( 8 );   the cold circuit ( 9 ) of an intermediate cooler ( 10 );   an expansion valve ( 11 );   a second exchanger ( 12 ) having a volume ( 31, 71 ) for the circulation of a coolant ( 21 ) in a heat-exchange relationship with the refrigerant ( 5 );   the inlet ( 13 ) of the hot circuit ( 14 ) of the intermediate cooler ( 10 ); the air conditioning device ( 1 ) being characterized in that the second exchanger of type ( 12 ) comprises an expansion volume for the coolant ( 21 ).

FIELD OF THE INVENTION

The present invention concerns the field of air conditioning and more particularly air conditioning circuits with transcritical operating cycle.

BACKGROUND OF THE INVENTION

Air conditioning devices for the passenger compartment of a vehicle are in widespread use, whatever the drive train of the vehicle. In the conventional way, an air conditioning device operates in accordance with a subcritical operating cycle of vapor compression employing a fluid such as R134a (tetrafluoreethane-1,1,1,2). A thermodynamic cycle is said to be subcritical when it operates below the critical temperature of the fluid. The critical temperature of a fluid is its maximum temperature in the liquid phase, whatever the pressure, i.e. the temperature at its critical point.

The use of fluids such as R134a will soon be prohibited because of its high greenhouse effect. Of the alternatives, carbon dioxide (CO₂), also designated R744, seems to be the most promising replacement for future air conditioning circuits. However, because of the low critical temperature (31 degrees Celsius) of CO₂, an air conditioning circuit employing CO₂ must adopt a transcritical operating cycle, i.e. one involving temperatures/pressures greater than the critical temperature/pressure of the fluid. The hardware usually employed for circuits with subcritical operating cycle is not suitable for transcritical operating cycles and therefore has to be redesigned.

In the conventional way, an air conditioning circuit with transcritical operating cycle comprises a rotary compressor driven, via a clutch, by a rotating element of the engine of the vehicle. Referring to FIG. 1, this compressor 60 compresses a refrigerant and directs it to a gas cooler 61 beside a fan. The fan forces a flow of air through the gas cooler 61 in order to evacuate maximum calories from the compressed fluid. The refrigerant is then directed toward the cold circuit of an internal exchanger 62 in which the refrigerant gives up more of its heat to a portion of the circuit corresponding to the hot circuit of the internal exchanger 62. The refrigerant cooled in this way is then directed toward a expansion valve 63 in which the refrigerant is expanded and which directs it toward a “chiller” (or water cooler) type exchanger 64. The “chiller” type exchanger 64 is connected to a cooling circuit 65 in which circulates a coolant exchanging heat with the refrigerant. The cooling circuit also includes an expansion vessel the function of which is to provide an expansion volume for absorbing variations in the volume of the coolant.

Because motor vehicle manufacturers wish to offer compact vehicles at the lowest possible price, there exists a requirement for compact and economical air conditioning circuits with transcritical operating cycle.

OBJECT OF THE INVENTION

An object of the invention is to reduce the overall size and the manufacturing and assembly costs of an air conditioning circuit with transcritical operating cycle.

SUMMARY OF THE INVENTION

To this end, there is provided an air conditioning device with transcritical operating cycle, comprising a circuit conveying a refrigerant and successively connecting:

-   -   the outlet of a compressor;     -   a gas cooler;     -   the cold circuit of an intermediate cooler;     -   an expansion valve;     -   a second exchanger of the air conditioning device having a         volume for the circulation of a coolant in a heat-exchange         relationship with the refrigerant;     -   the inlet of the hot circuit of the intermediate cooler. The         outlet of the hot circuit of the intermediate cooler is         connected to the inlet of the compressor.

According to the invention, the second exchanger comprises an expansion volume for the coolant.

This reduces the overall size of the assembly comprising the second exchanger and the expansion vessel by merging these two components. The risk of fluid leaking is also reduced by a reduction in the number of pipes. Finally, the manufacturing and assembly operations are simplified, all of the above resulting in a device that is more reliable, more compact and less costly than previous solutions.

The invention also comprises a second exchanger for an air conditioning circuit with transcritical operating cycle, comprising a bundle of tubes for circulating a refrigerant that extend in a volume for circulation of a refrigerant fluid. The second exchanger includes an expansion volume for the coolant.

The circulation volume of the coolant of an exchanger of the above kind is advantageously of substantially parallelepipedal shape and is delimited by a body comprising a first molded element and a second element clipped to the first. This assembly method is particularly economical and reliable.

According to one particular embodiment, the first element has a substantially parallelepipedal shape and the second element is substantially plane.

Alternatively, the first element and the second element are of substantially parallelepipedal shape.

Thus it is possible to propose exchangers for air conditioning circuits with transcritical operating cycle having two different coolant circulation volumes and a large number of common parts, which contributes to reducing the unit cost of each exchanger.

Finally, at least one of the elements comprises at least one groove receiving the flanks of a manifold of the bundle of tubes for circulation of the refrigerant.

This makes it possible to facilitate the relative positioning of the various components of the second exchanger during assembly and therefore reduces its manufacturing cost.

Other features and advantages will emerge from a reading of the following description of nonlimiting embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the appended drawings, in which:

FIG. 1 is a diagrammatic representation of a prior art air conditioning circuit with transcritical operating cycle;

FIG. 2 is a diagrammatic representation of an air conditioning circuit with transcritical operating cycle in accordance with the invention;

FIG. 3 is a perspective view of a first embodiment of a second exchanger according to the invention;

FIG. 4 is a perspective view of the exchanger from FIG. 3 rotated 90°;

FIG. 5 is an exploded perspective view of the exchanger from FIG. 4;

FIG. 6 is a section of the exchanger from FIG. 4 taken along the line VI-VI;

FIG. 7 is a perspective view of a second embodiment of a second exchanger according to the invention;

FIG. 8 is a perspective view of the exchanger from FIG. 7 rotated 90°;

FIG. 9 is an exploded perspective view of the exchanger from FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 2, the air conditioning device 1 with transcritical operating cycle is mounted in an engine compartment 2 of an internal combustion engine vehicle 3 (not shown).

The device 1 comprises a circuit 4 conveying a refrigerant 5, here CO₂, in a direction represented by the arrows. The circuit 4 connects successively:

-   -   the outlet 6 of a compressor 7;     -   a gas cooler 8;     -   the cold circuit 9 of an intermediate cooler 10;     -   an expansion valve 11;     -   a second exchanger 12 of the air conditioning device; and     -   the inlet 13 of the hot circuit 14 of the intermediate cooler         10.

The outlet 15 of the hot circuit 14 of the intermediate cooler 10 is, for its part, connected to the inlet 16 of the compressor 7.

A cooling circuit 20 conveys a coolant 21, here water containing glycol, by means of a circulation pump 22. The circuit 20 comprises a fluid/air heat exchanger 23 through which a fan 24 forces a flow of air intended for the passenger compartment of the vehicle 3. The coolant 21 penetrates into the second exchanger 12 in order to lose calories absorbed by the change of state of the refrigerant 5 in the second exchanger 12.

The second exchanger 12 could be used as a “chiller” or water cooler type exchanger. In such use, this type of exchanger functions as an exchanger able to produce cold for exchange with a coolant in another circuit of the motor vehicle, in particular when the latter includes batteries.

The second heat exchanger could also be used as a condenser type exchanger or as a gas cooler type exchanger cooled with a coolant (for example water containing glycol).

A first embodiment of the second exchanger 12 will now be described with reference to FIGS. 3 to 5.

The second exchanger 12 comprises a body 30 of substantially parallelepipedal shape delimiting an interior volume 31 containing a tube bundle 50. The body 30 comprises a first molded element 32 of substantially parallelepipedal shape on which is mounted a substantially plane second element 33. The elements 32 and 33 are fastened to one another by a plurality of clips 34 integral with the second element 33. The first element 32 includes an open face 35 and is provided with a plurality of exterior ribs 36 increasing its resistance to pressure. The first element 32 comprises a first internal peripheral groove 37 and an identical second groove 38. The grooves 37 and 38 are respectively at the upper end 39 and at the lower end 40 of the first element 32. The first element 32 also comprises first and second tubular connectors 41 and 42 respectively leading into an upper portion and a lower portion of the interior volume 31. As can be seen in the figures, the connectors 41 and 42 project on two opposite faces of the first element 32, one in the vicinity of the upper end 39 and the other in the vicinity of the lower end 40. A portion 43 of substantially parallelepipedal shape is connected by its base to the upper end 39 of the first element 32. The portion 43 is in fluid communication with the volume 31 because its base is open. A plug 44 situated on the face opposite the base of the portion 43 enables access to the internal volume 43.1 of the portion 43.

The second element 33 comprises a first tubular connector 45 and a second tubular connector 46 leading into the volume 31 and respectively facing the grooves 37 and 38.

Here the tube bundle 50 comprises seven parallel tubes 51 of rectangular section. The tubes 51 comprise crenellations 51.1 that increase the exchange area of the tubes with the medium surrounding them. The tubes 51 extend in the volume 31 from an inlet manifold 52 to an outlet manifold 53. Each of the manifolds 52 and 53 has a substantially parallelepipedal shape and a respective sealing element 54 and 55 nesting in the tubular part of the connectors 46 and 45 respectively.

During the manufacture of the second exchanger 12, the flanks of the manifolds 53 and 54 of the tube bundle 50 are placed in the respective grooves 38 and 37 of the first element 32. The second element 33 is then offered up so that the sealing elements 54 and 55 engage in the tubular parts of the connectors 46 and 45 respectively. The second element 33 is then brought into contact with the first element 32 and the elements 32 and 33 are fastened together by means of the clips 34. The second exchanger 12 constructed in this way therefore comprises a tube bundle 50 extending in an interior volume 31 between the two manifolds 52 and 53. The second exchanger 12 also comprises the internal volume 43.1 of the portion 43 in fluid communication with the volume 31.

The second exchanger 12 is connected to the air conditioning device 1 so that the refrigerant 5 at the outlet from the expansion valve 11 enters the inlet manifold 52 via the connector 46 and leaves the outlet manifold 53 via the connector 45. The inlet of the exchanger 23 is connected to the connector 42 and the outlet of the exchanger 23 is connected to the connector 41. In operation, the expanded refrigerant 5 evaporates in the tubes 51 of the tube bundle 50 and cools the coolant 21 circulated in the interior volume 31 by the circulation pump 22. In the event of variation of the volume of coolant 21 caused by a change in ambient pressure or a large quantity of heat to be evacuated, the volume 43.1 allows the expansion of the coolant 21. In effect, the volume 43.1 being situated above the connector 41 of the outlet for the coolant 21, the latter is little if at all occupied by the coolant 21 and forms an expansion volume for the latter.

Elements identical or analogous to those described above carry a reference number identical to the latter in the following description with reference to FIGS. 7 to 9 of a second embodiment of the invention.

The body 30 of the second exchanger 12 is of substantially parallelepipedal shape and comprises a molded first element 32 of substantially parallelepipedal shape open on one of its faces. A second element 70 that is also substantially parallelepipedal comprises an open face on which the open face of the element 32 is mounted. The bodies 32 and 70 thus define an interior volume 71 for circulation of the coolant 21. The elements 32 and 70 are fastened to one another by a plurality of clips 34. The connection between the two elements 32 and 70 can be effected by means of clips, screws, induction welding or vibration welding. The second element 70 is provided with a plurality of exterior ribs 36 increasing its resistance to pressure and a first internal peripheral groove 72 and a second internal peripheral groove 73 identical to the groove 72. The grooves 72 and 73 are respectively situated at the upper end 74 and at the lower end 75 of the second element 70. The second element 70 comprises a first tubular connector 45 and a second tubular connector 46 leading into the volume 71 facing the grooves 72 and 73 respectively.

Here the tube bundle 80 comprises fourteen tubes 51 extending in the volume 71 from the inlet manifold 52 to the outlet manifold 53.

During manufacture of the second exchanger 12, the flanks of the manifolds 53 and 54 of the tube bundle 80 are placed in the grooves 38 and 37 respectively of the first element 32. The second element 70 is then offered up so that the grooves 73 and 72 face the flanks of the manifolds 53 and 54. In this position, the sealing elements 54 and 55 engage in the tubular parts of the connectors 46 and 45 respectively. The second element 70 is then brought into contact with the first element 32 and the elements are clipped together. The second exchanger 12 constructed in this way therefore comprises a tube bundle 80 offering the exchange area of fourteen tubes 51. The manufacture of the second exchanger according to this second embodiment employs many elements common to or identical with the first embodiment, resulting in reduced manufacturing and tooling costs.

Of course, the invention is not limited to the embodiments described but rather encompasses any variant within the scope of the invention as defined by the claims.

In particular:

-   -   although the circuit here connects directly the various         components of the air conditioning device, the invention applies         equally to components connected to one another via other         components such as for example a desiccator, control or         regulation members, valves, etc.;     -   although here the refrigerant is CO₂, the invention applies         equally to other types of refrigerants able to operate with         transcritical operating cycle;     -   although here the coolant is water containing glycol, the         invention applies equally to other types of coolant such as for         example alcohol, salt water, ammonia or ammonium chloride;     -   although here the elements constituting the body of the second         exchanger are produced by a molding process, the invention         applies equally to other methods of manufacturing the elements         such as for example pressing, forming, welding or machining;     -   although here the elements of the body are clipped to one         another, the invention applies equally to elements connected to         one another by other assembly means such as for example welding,         screwing, gluing;     -   although here the connectors mounted on the body of the second         exchanger are tubular, the invention applies equally to other         types of connectors such as for example bayonet connectors or         cartridge type connectors;     -   although here the tubes of the tube bundle are crenellated and         seven or fourteen in number, the invention applies equally to         tubes of any shape in different numbers, such as for example         smooth tubes. 

1. An air conditioning device with transcritical operating cycle, the device comprising: a circuit conveying a refrigerant and successively connecting: an outlet of a compressor, a gas cooler, a cold circuit of an intermediate cooler, an expansion valve, a second exchanger having a volume for the circulation of a coolant in a heat-exchange relationship with the refrigerant, and an inlet of the hot circuit of the intermediate cooler, the outlet of the hot circuit of the intermediate cooler being connected to the inlet of the compressor, wherein the second exchanger comprises an expansion volume for the coolant.
 2. The device as claimed in claim 1, wherein the expansion volume of the second exchanger also includes an access plug.
 3. An exchanger for an air conditioning device with transcritical operating cycle, comprising: a bundle of tubes for circulating a refrigerant that extend in a volume for circulation of a coolant; and an expansion volume for the coolant.
 4. The exchanger as claimed in claim 3, further comprising an access plug to the expansion volume for the coolant.
 5. The exchanger as claimed in claim 3, wherein the volume for circulation of the coolant is of substantially parallelepipedal shape and is delimited by a body comprising a first element and a second element clipped to the first element.
 6. The exchanger as claimed in claim 5, wherein the first element has a substantially parallelepipedal shape and the second element is substantially plane.
 7. The exchanger as claimed in claim 5, wherein the first element and the second element are of substantially parallelepipedal shape.
 8. The exchanger as claimed in claim 5, wherein at least one of the elements comprises at least one groove receiving the flanks of a manifold of the bundle of tubes for circulation of the refrigerant. 